1. Technical Field
The present invention relates to a laser source device, a wavelength conversion element, a method of manufacturing a wavelength conversion element, a projector, and a monitoring device.
2. Related Art
Currently, many optical apparatuses such as projectors include high-pressure mercury lamp as illumination source. The high-pressure mercury lamp used in these apparatuses can provide high-output light, but has disadvantages such as limited color reproducibility, difficulty in immediate turning on, and short life. For these reasons, a laser source device is expected to be employed as a high-output light source in place of the high-pressure mercury lamp.
A laser source device including resonator and wavelength conversion element has been proposed as a high-output laser source device (see JP-A-5-75196, for example). The laser disclosed in JP-A-5-75196 (laser source device) has a laser material (active layer), a wavelength conversion element, and other components between input mirror and output coupler. When energy is supplied to the laser material from diode laser source for excitation, laser beam having fundamental wavelength is generated and reciprocates between the input mirror and the output coupler. The resonator is provided between the input mirror and the output coupler. The fundamental wavelength laser beam amplified thereat is converted into laser beam having conversion wavelength by the wavelength conversion element. The laser beam having conversion wavelength is extracted through the output coupler to obtain high-output laser beam having desired wavelength.
The laser disclosed in JP-A-5-75196 further includes a polarizing unit (Brewster plate) within the resonator. In this structure, the polarization condition of laser beam within the resonator is controlled by the polarizing unit such that laser beam having fundamental wavelength can be resonated in a preferable manner. The wavelength conversion element has polarization dependency, and thus the wavelength conversion element can provide preferable function by controlling the polarization condition of laser beam.
As discussed, the laser disclosed in JP-A-5-75196 emits high-output laser beam having desired wavelength. However, the laser still has several points to be improved in view of increasing efficiency and output.
According to the laser shown in JP-A-5-75196, the polarizing unit is disposed within the resonator, and laser beam enters the polarizing unit every time the beam reciprocates within the resonator. In this case, a part of the entering laser beam is reflected in unexpected directions due to concaves and convexes of the surface of the polarizing unit or the like, or absorbed by the polarizing unit. As a result, utilization efficiency of laser beam decreases.
For increasing output of laser beam, a plurality of laser beams emitted from a plurality of light emission units can be combined before emission. In this structure, however, arrangement of components such as the wavelength conversion elements and polarizing units provided for the respective light emission units in appropriate positions for the emission units requires considerable labors, and thus the const rises. On the other hand, in the structure having the common components such as the wavelength conversion element and polarizing unit for the plural light emission units, the positions of the components need to be determined considering polarization dependency of the wavelength conversion element. In this case, the degree of freedom for disposing the components considerably lowers, and constitution of the laser having this structure becomes difficult.